1. Field of the Invention
The present invention relates to air ventilation systems and, more particularly, is directed to an improved air distribution panel for air ventilation hoods of the type used over open cooking surfaces or grills for removing heated, grease laden or otherwise contaminated air from within the kitchen area.
2. State of the Prior Art
The present invention relates to a particular type of ventilating hood known in the industry as a "make-up air" hood and exemplified by this applicant's disclosure in U.S. Pat. No. 4,186,727. This type of ventilating hood is characterized by a horizontally extended make-up air hood, a horizontally extended exhaust hood, and a longitudinally extended divider wall between the two hoods. The make-up hood is provided with an inlet connected by suitable ducting to the exterior of the building for admitting make-up air into the make-up hood. The exhaust hood is also connected to an outlet for exhausting contaminated air to the exterior atmosphere. The make-up hood includes walls which, together with the divider wall and the air diffuser, define a make-up plenum. Air is forced into the make-up air plenum and drawn from the exhaust air plenum by means of suitable fans to create a pressure differential across the bottom of the dividing wall such that make-up air flows downwardly through the make-up plenum, discharging downwardly along the divider wall to a region below the lower end of the divider wall, turns horizontally toward the exhaust hood and then flows upwardly thereinto. Vortex baffles are typically provided in the exhaust plenum to bring about efficient mixing of make-up air with contaminated air rising from the underlying cooking surface, which mixed air then passes through grease filters and is exhausted to the outside. The make-up plenum is further provided with air distribution panels extending longitudinally within the make-up hood and disposed above the bottom of the divider wall. Downward flow of air from the make-up plenum is restricted by the air distribution panels in order to maintain a positive pressure in the make-up plenum and thereby evenly distribute the flow of make-up air along the length of the make-up hood.
The ventilating hood is normally dimensioned such that the exhaust hood extends substantially over the entire cooking surface while the make-up portion of the hood overlies an area in front of the stove or grill where cooks and other kitchen personnel normally stand while working. It was found in practice that only a portion of the downwardly discharging make-up air returns towards the exhaust side of the hood as intended. A substantial portion of the make-up air stream would instead discharge downwardly onto the heads of personnel standing in front of the cooking surface. Such downward flow of outside air could be substantially colder or warmer than air in the kitchen and is therefore not only uncomfortable to personnel working underneath the hood, but also interferes with the efficient heating or air-conditioning of the kitchen. Further still, such divided flow of make-up air reduces the efficiency of the ventilating hood in extracting contaminated air.
To avoid this problem, it was found necessary to partially close off the air distribution panels such that make-up air was discharged downwardly only in close proximity to the dividing wall where the make-up air would be effectively captured by the negative pressure in the exhaust hood and would therefore flow under the lower edge of the dividing wall as intended. The prior art air distribution panels thus consist of a rectangular frame in which is disposed a solid panel extending the full length, but only approximately half the width of the frame. Air flow through the remaining opening in the frame is restricted by means such as a perforated plate and one or more layers of screen fabric having a mesh smaller than the openings in the plate. To maintain a positive air pressure in the make-up plenum. The distribution panels are mounted within the make-up hood with the open side of the panel (i.e., the portion of the panel which includes the perforated plate and the mesh) adjacent to the dividing wall of the hood, while the closed side of the distribution panel is adjacent a wall of the make-up hood opposite the dividing wall. Downward flow of make-up air is thus limited to a region near the dividing wall and extending the full length of said dividing wall.
While this approach solved the problem of discharge of make-up air into the kitchen area and onto kitchen personnel, it also significantly reduced the volume of make-up air flowing into the exhaust hood, thus reducing the efficiency of the ventilating system.